Recently, a variable displacement compressor used in an automobile air conditioner is being widely researched. The variable displacement compressor is a device that varies an inclination angle of a swash plate using a control valve and controls the stroke of a piston according to variation in a thermal load to thereby accomplish precise temperature control, and simultaneously, continuously varies the inclination angle to attenuate abrupt torque fluctuation of an engine due to the compressor, thereby enabling a smoother drive.
An example of a conventional variable displacement compressor as described above is disclosed in Korean Patent Publication No. 2002-0038464, and the structure is shown in FIG. 1.
As shown in FIG. 1, the conventional variable displacement compressor includes a cylinder block 12 having a plurality of cylinder bores 12a parallelly and longitudinally formed at an inner periphery thereof, a front housing 11 sealed in the front of the cylinder block 12, and a rear housing 13 sealed in the rear of the cylinder block 12 by a valve plate 14a. 
A swash plate chamber 15 is disposed inside the front housing 11. One end of a drive shaft 16 is rotatably supported adjacent to the center of the front housing 11, and the other end of the drive shaft 16 passes through the swash plate chamber 12 to be supported by a bearing 17 disposed in the cylinder block 12.
In addition, the drive shaft 16 includes a lug plate 23 and a swash plate 25. A spring is interposed between the lug plate 23 and the swash plate 25 to resiliently support the swash plate 25.
The lug plate 23 includes a pair of power transmission support arms integrally projecting from its one surface, each of which has a guide hole punched straight through a center thereof. And, the swash plate 25 has a ball 26 formed at its one side, such that the ball 26 of the swash plate 25 slides in the guide hole of the lug plate 23 as the lug plate 23 rotates, thereby varying the inclination angle of the swash plate 25.
Further, an outer periphery of the swash plate 25 is slidably inserted into each piston 21 via shoes 27.
Therefore, as the swash plate 25 rotates in an inclined state, the pistons 21 inserted into the periphery thereof via the shoe 27 reciprocate in the cylinder bores 12a of the cylinder block 12, respectively.
In addition, the rear housing 13 has a suction chamber 31 and a discharge chamber 32, and a valve plate 14a interposed between the rear housing 13 and the cylinder block 12 has a suction port 33 and a discharge port 35 corresponding to the cylinder bores 12a. The suction chamber 31 and the discharge chamber 32 are connected to the exterior of the compressor through an external refrigerant circuit (not shown).
Meanwhile, an oil separator 39 is installed in the rear of the drive shaft 16 and surrounded by an oil chamber 40. A communication aperture 42 is formed in the drive shaft 16 to connect the swash plate chamber 15 with the oil separator 39. The oil separator 39 has a cylindrical cap shape, and includes a groove 39b formed in a circumferential direction thereof.
When the compressor actually operates, pressure in the swash plate chamber 15 is varied in response to manipulation of a control valve 38 (for example, from low pressure to high pressure) so that the refrigerant remaining in the swash plate chamber 15 is discharged to the suction chamber 31 through an additional exhaust path 45.
As described above, the refrigerant gas moves from the swash plate chamber 15 to the suction chamber 31 via the interior of the oil separator 39 through the additional exhaust path 45. At this time, a portion of the refrigerant gas passing through the interior of the oil separator 39, adjacent to an inner periphery of the oil separator 39, is rotated together with the oil separator 39. As a result of the rotation, misty oil contained in the refrigerant gas is centrifugally separated from the refrigerant gas.
As described above, the oil separated by the oil separator 39 slides to a rear end of the oil separator 39 along its inner periphery. Then, the oil is discharged to the exterior of the oil separator 39 through a gap or the groove 39b between a front end of the oil separator 39 and a valve/port forming body 14 by means of the centrifugal force due to rotation of the oil separator 39, and stays in an oil chamber 40.
In addition, the oil is continuously introduced into a suction path 37 through a communication path 40a, and returned to the swash plate chamber 15 by a flow of the refrigerant gas. Therefore, oil in the swash plate chamber 15 becomes abundant to perform lubrication of the compressor well.
Meanwhile, after separation of oil in the oil separator 39, a portion of the refrigerant gas is introduced into the suction chamber 31 through a path 41, and sequentially passes through a compression chamber 22 and the discharge chamber 32 to be discharged to an external refrigerant circuit.
The above publication discloses various constitutions of the oil separator 39.
However, the conventional variable displacement compressor needs a separate oil separating device such as an oil separator, and a separate space for the oil separator, thereby causing large restriction in design and assembly.